Reaction of hexafluoropropene oxide with fluorinated carboxylic acid fluorides

ABSTRACT

Process for the preparation of halogenated carboxylic acid fluorides, in which a carboxylic acid fluoride is reacted with hexafluoropropene oxide in the presence of a catalyst system composed of an alkali metal fluoride, a carboxylic acid dinitrile and at least one ether of the formula CH3O-(CH2CH2O)z-CH3 (V) in which z denotes an integer from 2 to 6.

Fluorinated acid fluorides of the general formula ##STR1## in whichR_(f) denotes a halogen-containing, in most cases fluorine-containing,radical, preferably perfluoroalkyl, branched or unbranched and having1-10 carbon atoms and n denotes an integer from 1 to 5 are prepared byreacting carboxylic acid fluorides of the general formula

    R.sub.f --COF                                              (II)

in which R_(f) has the abovementioned meaning with hexafluoropropeneoxide (HFPO). The reaction is carried out in the presence of a catalystand takes place in accordance with the following equation. ##STR2## Asummarizing description of this reaction, including the catalysts used,has been given in Angew. Chem. Int. Ed. Engl. 24, 161-178 (1985). One ofthe catalysts described therein is a mixture of potassiumfluoride/adiponitrile and tetraglyme (tetraethylene glycol dimethylether). The mixture has hitherto only been employed for the synthesis ofspecial compounds of the general formula (I), for example ##STR3## Oneadvantage of this catalyst mixture is stated to be a maximum yield ofthe desired product of the general formula (I), with the simultaneousavoidance of byproducts of the type ##STR4## which are formed by thereaction of HFPO with itself. It is stated as a further advantage ofthis catalyst system that potassium fluoride, which is cheap, can beemployed as the source of fluoride ions.

The yields of the desired compounds of the general formula (I) were,however, below 50% when this catalyst system was employed, so that itsuse cannot in general be regarded as advantageous.

The reaction of acid fluorides of the general formula

    R--COF                                                     (III)

in which R is the group CCl₃ or X--(CF₂)_(p), X being hydrogen, bromineor SO₂ F and p being an integer from 1 to 6, with HFPO has hitherto beencarried out in accordance with the instructions in the presence ofcatalysts containing costly cesium fluoride (Angew. Chem. Int. Ed. Engl.24, 161 (1985)).

It was therefore required to find a catalyst system which can beemployed generally for this reaction and which can replace the expensivecesium fluoride and which enables good utilization of the HFPO.

The invention relates to a process for the preparation of halogenatedcarboxylic acid fluorides by reacting a carboxylic acid fluoride withhexafluoropropene oxide in the presence of a catalyst, in which processa carboxylic acid fluoride of the formula

    R--COF                                                     (III)

in which R is the group CCl₃ or X--(CF₂)_(n), X representing a hydrogenatom, a bromine atom or a fluorosulfonate radical and n denoting aninteger from 1 to 6, is reacted with hexafluoropropene oxide in thepresence of a catalyst system composed of an alkali metal fluoride, acarboxylic acid dinitrile and at least one ether of the formula

    CH.sub.3 O--(CH.sub.2 CH.sub.2 O).sub.z --CH.sub.3         (V)

in which z denotes an integer from 2 to 6.

It is preferable to employ a carboxylic acid fluoride of the formula(III) in which R has the meaning mentioned above and n denotes aninteger from 2 to 4.

It was surprising that the catalyst system employed in accordance withthe invention

produces high conversions of the acid fluoride of the general formula(III),

gives a high utilization of HFPO and

can be employed generally and then gives yields which are markedlyhigher than the yields hitherto achieved in the case of certaincompounds or at least achieves the yields which it was possible toachieve using the cesium fluoride catalysts.

In addition, the reaction system is substantially less sensitive tomoisture than the other known systems. The yields achieved are, ingeneral, between 65 and 80%. The acid fluorides obtained by the processaccording to the invention are valuable intermediate products in thefield of the organic chemistry of fluorine. In particular, they areemployed for the preparation of vinyl ethers of the general formula##STR5## in which R has the abovementioned meaning and q can be aninteger from 0 to 2.

The catalyst system used is a mixture of an alkali metal fluoride, acarboxylic acid dinitrile and at least one ether of the formula (V).Alkali metal fluorides are sodium fluoride and, preferably, potassiumfluoride. The carboxylic acid dinitrile used can be the dinitriles ofsaturated aliphatic dicarboxylic acids having 5 to 8 carbon atoms,preferably adipodinitrile. Ethers of the formula (V) are polyethyleneglycol dimethyl ether, preferably the dimethyl ether of triethylene orpentaethylene glycol, but particularly the tetra-compound (tetraglyme).The three components of the catalyst system are employed in the ratio(5-30):(50-80):(5-40), preferably (8-20):(55-70):(10-30) percent byweight, relative to the system. It is advantageous for the alkali metalfluoride to be thoroughly dried and finely pulverized before use. Acarboxylic acid dinitrile of commercially available purity can be usedwithout further pretreatment. The ether, for example tetraglyme, canalso be employed without further treatment in the purity available. Itis also possible to use tetraglyme in the form of a distillation cutcomposed of oligomeric ethylene glycol dimethyl ethers together with themain component tetraglyme. It is also not disadvantageous for thereaction according to the invention if the tetraglyme contains a smallamount of the monomethyl ether component. Thus, for example, thetetraglyme used in Example 1 is composed of 17% area of triglyme, 65%area of tetraglyme, 12% area of pentaglyme, 1% area of hexaglyme and 5%area of triglycol monomethyl ether, determined by gas chromatography.The catalyst system is used in an amount of 5 to 45, preferably 10 to40, % by weight, relative to the carboxylic acid fluoride employed.

The reaction according to the invention is carried out by initiallyplacing the catalyst mixture in a vessel which can, for example, be madeof glass or stainless steel and which is equipped with an effectivestirrer, and adding the acid fluoride of the general formula (III). Therequired amount of HFPO is then introduced in the form of gas. It isadvantageous to stir vigorously during the whole reaction. The reactioncan be carried out under reduced pressure, elevated pressure or normalpressure, but normal pressure or elevated pressure, in general up to 20bar, preferably up to 10 bar, is preferred. The reaction temperature canbe between -30 and +100° C., temperatures between 0° and 60° C. beingpreferable.

EXAMPLES

(1) 90 g of potassium fluoride, 350 m1 of adiponitrile and 100 mI oftetraglyme (wide boiling range) were put into a 5 liter glass autoclaveequipped with a stirrer, and 2,050 g of H--CF₂ --CF₂ --COF wereintroduced into the mixture. HFPO was then injected, with vigorousstirring, whereupon an exothermic reaction set in. The pressure was keptat 2-3.5 bar and the internal temperature at 40°-50° C. Altogether,2,900 g of HFPO were reacted. The mixture was stirred overnight at roomtemperature, in the course of which the pressure fell to less than 0.5bar. The contents of the autoclave were subjected to simpledistillation. This gave 4,430 g of a colorless distillate which had aboiling point of 30°-130° C. and which, according to gas chromatographyon a sample esterified with methanol had the following composition:

    __________________________________________________________________________                         % by                                                                          weight                                                                            b.p.    yield*                                       __________________________________________________________________________     ##STR6##         m = 1 m = 2                                                                       11   55-58° C. 116-120° C.                                                  discarded                                    ##STR7##        n = 1 n = 2 n = 3                                                                 70 16  1                                                                           72-75° C. 126-130° C.                                                  71% 11%                                      __________________________________________________________________________     *relative to HCF.sub.2CF.sub.2COF employed                               

The conversion of H--CF₂ --CF₂ --COF was over 90%.

(2) (Comparison) A catalyst mixture composed of 30 g of cesium fluorideand 100 mI of tetraglyme as well as 880 g of H--CF₂ --CF₂ --COF wasinitially placed in a 2 liter glass autoclave equipped with a stirrer,and was reacted as in Example 1 with 1,975 g of HFPO at 23°-29° C. and apressure of 3.2-3.6 bar. A residual pressure of 1.6 bar was stillpresent after stirring overnight. Working up as in Example 1 gave thefollowing yields:

    __________________________________________________________________________     ##STR8##        m = 1 m = 2                                                                       b.p.  55-58° C. b.p. 116-120° C.                                        520 g 223 g                                       ##STR9##        n = 1 n = 2                                                                       b.p.  72-75° C. b.p. 126-130° C.                                        1,067 g  556 g                                                                     57% 20%                                     __________________________________________________________________________

The conversion of H--CF₂ --CF₂ --COF was approx. 90%.

(3) 1,416 g of Br--CF₂ --COF, 50 g of potassium fluoride, 300 ml ofadiponitrile and 120 ml of tetraglyme were initially placed in theapparatus of Example 1. The exothermic reaction with 1,550 g of HFPO iscarried out at 45°-50° C. and a pressure of 2-2.2 bar. When theintroduction of HFPO was complete, the pressure fell rapidly to 0 bar.Distillation of the contents of the autoclave gave the following: 2,106g of the compound ##STR10## in which n =1 (=77%), b.p. 71°-76° C. and 62g of the compound in which n =2 (=1.5%), b.p. 128° C.

(4) 15 g of potassium fluoride, 100 m1 of adiponitrile and 40 m1 ©ftetraglyme were initially placed in a glass flask equipped with arefrigerated condenser (-78° C.), a thermometer and a gas inlet tube.This mixture was cooled and 788 g of Br--CF₂ --CF₂ --COF previouslycooled to -5° C. were added. 680 g of HFPO were then introduced in theform of gas under normal pressure in the course of 415 minutes, and theinternal temperature of the mixture was kept below 50° C. The followingacid fluorides were isolated by distillation:

    __________________________________________________________________________     ##STR11##          b.p. 97-99° C.,                                                                 1,065 g                                                                            78%                                          ##STR12##          b.p. 147° C.,                                                                     151 g                                                                             8%                                         __________________________________________________________________________

(5) 90 g of potassium fluoride, 350 ml of adipodinitrile and 100 m1 oftetraglyme were initially placed in a glass flask equipped as in Example4. 2,465 g of CF₂ --CF₂ --O--SO₂ were then added dropwise, and thisisomerized immediately, in an exothermic reaction, to give FSO₂ --CF₂--COF. 4,370 g of HFPO were then introduced in the form of gas and theinternal temperature was kept below 50° C. during the introduction ofthe gas. The mixture was worked up by distillation. 3,745 g (79%) ofFSO₂ --CF₂ --CF₂ --O--CF(CF₃)--COF having a boiling point of 92°-94° C.were obtained.

(6) 29 g of potassium fluoride, 150 ml of adipodinitrile, 60 oftetraglyme and 1,400 g of CCl₃ --COF were initially placed in anapparatus as described in Example 4. 1,660 g of HFPO were thenintroduced in the form of gas in the course of 4.5 hours, the internaltemperature being kept below 37° C. by cooling. The reaction mixture wassubjected to a distillation under reduced pressure in which the internaltemperature was kept below 120° C. Crude yield of acid fluoride mixtures2,950 g. Fractional distillation under normal pressure gave thefollowing yields:

    __________________________________________________________________________     ##STR13##      n = 1 n = 2                                                                       b.p. 117-121° C., b.p. 161-163°                                          1,924 g   169 g                                                                   68.6%  4%                                    __________________________________________________________________________

(7) 5 g of potassium fluoride, 50 ml of adipodinitrile and 20 ml oftetraglyme were initially placed in the apparatus of Example 4 and 203 gof 5-H-octafluorovaleryl fluoride were added dropwise. 166 g of HFPOwere introduced in the form of gas in the course of 40 minutes, and theinternal temperature was kept at 25°-40° C. by cooling with ice.Stirring was continued for one hour at room temperature, and the mixturewas distilled under reduced pressure, whereby 317 g of distillate havinga boiling point of 43°-83° C./67 mbar were obtained. 39 g of substancecondensed in the cold trap (-78° C.) situated downstream. The distillateand the contents of the trap were combined. The composition wasdetermined by esterifying a sample with methanol. The mixture of estersshowed the following composition when subjected to analysis by gaschromatography:

    ______________________________________                                        approx.  4% area                                                                             ##STR14##                                                      approx.  4% area n = 0 approx. 80% area n = 1 approx.  8% area n =                           ##STR15##                                                      ______________________________________                                         240.5 g (≅71%) of H--(CF.sub.2).sub.5 --O--CF(CF.sub.3)--COF,     b.p. 115°-119° C., were isolated by distillation through a     packed column.

I claim
 1. A process for the preparation of halogenated carboxylic acidfluorides by reacting a carboxylic acid fluoride with hexafluoropropeneoxide in the presence of a catalyst, which comprises reacting acarboxylic acid fluoride of the formula

    R--COF                                                     (III)

in which is the group CCl₃ or X--(CF₂)_(n), X representing a hydrogenatom, a bromine atom or a fluorosulfonate radical and n denoting aninteger from 1 to 6, with hexafluoropropene oxide in the presence of acatalyst system comprising an alkali metal fluoride, a carboxylic aciddinitrile and at least one ether of the formula

    CH.sub.3 O--(CH.sub.2 CH.sub.2 O).sub.z --CH.sub.3         (V)

in which z denotes an integer from 2 to
 6. 2. The process as claimed inclaim 1, wherein the carboxylic acid fluoride used is a compound of theformula (III) in which R has the meaning mentioned, but in which ndenotes 2, 3 or
 4. 3. The process as claimed in claim 1, wherein thealkali metal fluoride used is potassium fluoride.
 4. The process asclaimed in claim 1, wherein the carboxylic acid dinitrile used is adinitrile of a saturated aliphatic dicarboxylic acid having 5 to 8carbon atoms.
 5. The process as claimed in claim 4, wherein thecarboxylic acid dinitrile used is adipodinitrile.
 6. The process asclaimed in claim 1, wherein the ether of the formula (2) used is thedimethyl ether of triethylene, tetraethylene or pentaethylene glycol. 7.The process as claimed in claim 1, wherein the reaction is carried outat a temperature from -30° to +100° C.
 8. The process as claimed inclaim 7, wherein the reaction is carried out at a temperature between 0°and 60° C.
 9. The process as claimed in claim 1, wherein the componentsof the catalyst system are used in an amount composed of 5 to 30 % byweight of alkali metal fluoride, 50 to 80 % by weight of carboxylic aciddinitrile and 5 to 40 % by weight of ether, in each case relative to thecatalyst system.
 10. The process as claimed in claim 9, wherein thecomponents are employed in the ratio (8-20):(55-70):(10-30).
 11. Theprocess as claimed in claim 1, wherein the catalyst system is used in anamount of 5 to 45 % by weight, relative to the carboxylic acid fluoride.12. The process as claimed in claim 11, wherein an amount of 10 to 40 %by weight of the catalyst is used.
 13. A process for the preparation ofhalogenated carboxylic acid fluorides which comprises:reacting acarboxylic acid fluoride of the formula

    R--COF                                                     (III)

in which R is CCl₃ or X--(CF₂)_(n),wherein X is H, Br, or FSO₂, and n isan integer from 1 to 6,with hexafluoropropene oxide in the presence of acatalyst system consisting essentially of: (a) potassium fluoride, (b) acarboxylic acid dinitrile, and (c) at least one ether of the formula

    CH.sub.3 O--(CH.sub.2 CH.sub.2 O).sub.z CH.sub.3

in which z is an integer from 2 to
 6. 14. A process as claimed in claim13, wherein the dinitrile is a dintrile of a saturated aliphaticdicarboxylic acid having 5 to 8 carbon atoms.
 15. A process as claimedin claim 13, wherein the catalyst system consists essentially, based onthe weight of said catalyst system, of:(a) 5-30% by weight potassiumfluoride, (b) 50-80% by weight adiponitrile, and (c) 5-40% of saidether.